PhP url within an image help

I wish to place my youtube page in one of my little advertising boxes (which is an image btw) that came with a free template and it came with this code.

<a href="#"><img class="ads1" alt="" src="<?php bloginfo('template_url'); ?>/images/your-ads-125x125-black.jpg" /></a>

Lets say my youtube page is http://www.youtube.com.

Where in the above code would I put http://www.youtube.com?

I thought I had tried every possible way, but obviously I am not getting it.

Thanks for your help.